Questions are one of the reasons this forum is here
For the intake, AEM offers a air bypass valve for CAIs (could air intakes) that helps prevent hydrolock
I guess that if the pavement is really hot the air that the intake pulls up near the groung might be warmer than that pulled in by the stock intake near the hood.
The Tanabe Medalion Touring is a quiet exhaust that should give you a few more HP. More info
here you can also listen to an Si with it there.
cat-back exhaust: everything behind the catalitic converter is replaced
AEM CAI is about $300
Tanabe exhaust is about $700
Here's a picture of the tanabe medalion touring exhaust:
